Merge Join Problem

Hello,
I've got a problem with the merge join operator.

I'm trying to Join two tables using a left outer join.

Here are my tables :

TABLE AGENT
AGENT_CODE; REGION_ID; COUNTRY_ID
AA;01;01;
BB;01;01;
CC;01;02;
CC;02;02;
DD;01;01;

600 records in this table.

TABLE DELEGUE
AGENT_CODE; FIRST_NAME; LAST_NAME
AA; Maradona;Diego;
BB; Maradona;Diego;
DD; Zidane;Zinedine;

145 records in this table.

This is what i expect in my left outer join:
AGENT_CODE; REGION_ID; COUNTRY_ID;FIRST_NAME; LAST_NAME
AA;01;01;Maradona;Diego;
BB;01;01;Maradona;Diego;
CC;01;02;NULL;NULL
CC;02;02;NULL;NULL;
DD;01;01;Zidane;Zinedine

600 records in the destination table, with only 145 Not null first_name and last_name



The
issorted property has been set to true in the 2 sources tables, the
numkeyscolumns property is set to 1, and the join keys are both checked.
When i execute the sql query using the editor in sql server, the result is good, i've got what i've expected.
But
when i run the dataflow, the destination has got 600 records, but the
columns FIRST_NAME and LAST_NAME are not null only 8 times, the 592
other lines are NULL.
Could someone explain to me why i lost 145-8=137 FIRST_NAME and 145-8=137 LAST NAME ?
Thank you in advance.